1. Field of the Invention
The present invention relates to a tilt telescopic steering device that allows significant enhancement of the tilt holding force of a tilt telescopic column.
2. Description of the Related Art
As examples of the background art, Japanese Patent Application Laid-open Nos. 2005-7905 and 2005-125994 describe steering devices comprising an ordinary tilt telescopic adjustment mechanism in which tilt and telescopic stroke are fixed by a lever at one site.
The features of Japanese Patent Application Laid-open No. 2005-7905 are analyzed next as a concrete example of the foregoing. During tilt in Japanese Patent Application Laid-open No. 2005-7905, a shaft rod member 23 act as a support shaft, while a shaft rod member 18 and a movable bracket 4 pivot along a tilt long hole, in the up-and-down direction relative to the a fixed bracket 3. During a telescopic stroke, meanwhile, the movable bracket 4 is displaced relative to the shaft rod members 18, 23, in a front-rear direction, via a telescopic long hole 17 of the movable bracket 4. The rotation shaft for tilt is slidable during the telescopic stroke, but fixed during tilt. The shaft rod member 23, moreover, is slidably provided, although it is fixed during driving travel. Tilt telescopic fixing (locking) is carried out at one site by way of a lever 20 mounted on the shaft rod member 18.
In Japanese Patent Application Laid-open No. 2005-7905, having a tilt fulcrum A (center of rotation: shaft rod member 23), an action point B (lever fastening position: shaft rod member 18), and a force point C where the handle tilts, the force exerted on the force point C acts on the action point B (lever fastening position) with a high ratio. To increase the tilt holding force (force acting on the force point C) during lever fastening, therefore, it becomes necessary to increase the torque for fastening the lever at the action point B. Japanese Patent Application Laid-open No. 2005-125994 has the same problem.